In the art of sound detection, an underwater environment is an extremely difficult one in which to operate sophisticated electronic equipment. Many acoustic sensing devices include hydrophone sensors and any misalignment requires compensation using complex signal processing techniques. Many of these employ accelerometer or vane type hydrophones to compensate for misalignment but this results in flow-induced vibrations which create noise in the system. There is, therefore a need in the art for an acoustic sensing apparatus which is simple to fabricate, cost effective, versatile for application to various uses, and which eliminates the complicated signal processing now required for these type apparatus.
It is, therefore, in accordance with one aspect of the present invention an object to provide an acoustic sensing apparatus comprised of state-of-the-art materials but fabricated using conventional techniques and which, when deployed into a water environment, is configured in a manner which reduces hydrophone misalignment to an extent that complex signal processing is eliminated in obtaining sound source discrimination.
In accordance with another aspect of the invention it is an object to provide an apparatus including a hydrophone sensor array comprised of ring-mounted, quadrature-oriented sensors and a tensioned cable arrangement which maintains both vertical separation and horizontal position of the sensors such that simplified and conventional signal processing techniques may be employed for sound source discrimination in directions which are perpendicular to the sensor array axis, i.e., azimuthal discrimination.
According to still another aspect of the invention it is an object to provide an apparatus including a hydrophone sensor array in a configuration such that sound source discrimination in both azimuth and elevation may be achieved.
In accordance with another aspect of the invention it is an object to provide an apparatus which may be compactly stowed and deployed into the ocean via surface ship, aircraft, or any other of the known deployment techniques and which, upon being so deployed, will automatically and in a fail-proof manner be configured into the desired shape and orientation for effective operation.
According to another aspect of the invention it is an object to provide a sensing apparatus for use in an ocean environment which may be configured as a passive listening device or, alternatively, as a passive listening device with an active response threat.